This is kinda cool, from Paul Tan's detailed powertrain piece:
Both engines also adopt pistons with a “cavity-shaped” and optimised skirt design to minimise vibration and increase operating efficiency. Lightweight steel connecting rods are heat-forged in one piece for higher strength as well. A new grinding process known as plateau honing further lowers the friction level between the pistons and cylinders, along with the use of low viscosity 0W-20 oil. Additionally, regular (US-grade) unleaded 87 octane petrol can be used on both engines.